This invention relates to a magnetically driven shaft powered by a fuel cell.
The fundamental electrochemical processes involved in fuel cells are well understood. A fuel cell is an electrochemical device wherein an input fuel is catalytically reacted with an input oxidant at electrode interfaces that share a common electrolyte in the fuel cell, resulting in a flow of electrons as well as reaction product. Typically, the electrolyte is sandwiched between two thin electrodes, namely a porous anode and a porous cathode. Where the input fuel is hydrogen and the oxidant is oxygen, the fuel cell produces electricity and water. The basic process is highly efficient and, for those fuel cells fueled directly by hydrogen, pollution-free. Further, fuel cells can be assembled into stacks, of varying sizes, and so power systems have been developed to produce a wide range of output levels and thus satisfy numerous kinds of end-use applications, including electric motors.
In the description below, a xe2x80x9cfuel cell stackxe2x80x9d comprises one or more fuel cell units. Typically, a fuel cell stack comprises multiple fuel cell units stacked together and electrically connected in series.
U.S. Pat. No. 5,923,106 and U.S. Pat. No. 6,005,322 both issued to Isaak et al. disclose the use of a fuel cell to power an electric motor. The ""106 patent teaches a fuel cell (of no specific type or description) integrated inside the cylindrical main body of a electric motor, the cylindrical main body having a copper band inlaid on its outer surface. A second, larger cylinder or outer drum placed externally to the main body and concentric with it has a corresponding band of permanent magnets inlaid within its inner circumference. The top of the outer drum is attached to an output shaft. In operation, the fuel cell causes a direct electrical current to flow from positive leads attached in a circular array to one linear end of the copper band to negative leads attached in a circular array to the other linear end of the copper band. A magnetic field exists in the gap between the main body and the outer drum, and the action of the current at right angles to the magnetic field produces a force perpendicular to both axes causing the outer drum to rotate and therefore indirectly cause the output shaft also to rotate.
The ""322 patent discloses a variation of the fuel cell powered electric motor in the ""106 patent. In the electric motor of the ""322 patent, the outer drum is kept stationary and the fuel cell is permitted to rotate within it, rather than the other way around. In the ""322 patent, the output shaft is attached to the rotating fuel cell rather than to the outer drum, but otherwise the electric motors in the ""106 patent and the ""322 patent are essentially identical.
A fuel cell powered magnetically driven shaft assembly according to the invention is simpler in construction than similar prior art assemblies. It comprises: (a) a stationary fuel cell stack having a hollow core; (b) an electrically conductive sleeve lining the hollow core so as to define a cylindrical passage therethrough; and (c) a shaft extending through the sleeve passage and rotatable about the longitudinal axis of the shaft. The shaft is embedded with one or more magnets configured to produce a magnetic field extending substantially perpendicularly to the longitudinal axis of the shaft. Anodes of the fuel cell stack are connected to one end of the sleeve and cathodes are connected to the other end so as to provide a path for conducting electrons through the sleeve constrained in a direction parallel to the longitudinal axis of the shaft. Because the current flows perpendicularly through the magnetic field produced by the magnets, an electromagnetic force is produced in a direction which is tangential to the shaft, causing the shaft to rotate about its longitudinal axis.
The assembly may further comprise bearings for supporting the shaft while allowing it to rotate about its longitudinal axis.
The fuel cell stack can be composed of any type of fuel cell, although a xe2x80x9cproton exchange membranexe2x80x9d fuel cell is preferred given its relatively high power density and low operating temperature. The fuel cell stack is typically cylindrical, but the outside shape could vary to accommodate various containment spaces.
Such a fuel cell assembly is compact and readily adaptable for many uses, while being simple in construction and relatively inexpensive to manufacture. It has fewer moving parts than prior art assemblies and is less likely to require repair.